Margrethe Vestager may just consider this to be her worst month in office since she took over the mantle from Joaquín Almunia as the head of the European Commissioner for Competition back in 2014. In many respects, the watchdog she’s been leading ever since is the single most crucial regulatory element to preserving the very foundation of the European Union – the concept of the political block’s single market.

Because just shy of the fourth anniversary of her first big “win” in the role of the EC’s Competition Commissioner, Vestager got the rug pulled under her following the seminal success of Apple’s appeal to a 2016 ruling claiming it owes the equivalent of $15 billion in back taxes to Ireland – and the EU, by extent.

The difference between tax avoidance and fulfilling one’s fiduciary duty

Ireland, for its part, always insisted that isn’t true, but Brussels regulators never took issue with any discrepancies between their stories. If anything, the fact that they were a perfect fit for each other from day one actually added to the Commission’s suspicions of foul play.

In short, Ireland changed its corporate tax laws and a wide variety of related statues on numerous occasions over the first 13 or so years of the 21st century. The EC claimed it did so with the sole purpose of benefiting Apple at the expense of the rest of the bloc and in clear violation of the very spirit that made it join the European Union in the first place.

Basically, the European single market only works if everyone is paying tax on what they are earning, based on where they are doing the earning. A combination of loopholes identified by the Irish government and some clever legislation designed around those loopholes is what allowed Apple to continue paying an effective corporate tax rate of less than 3% on all of its EU earnings by declaring its profits in Ireland, disregarding dozens of markets in which they were actually made. Seeing how the EU gets a share of all tax, it was naturally less than thrilled with a $15 billion loophole in its laws – that’s a lot of billions to miss out on because one of your members essentially said it’s all good. After all, Ireland’s goal wasn’t to create more tax revenue, it was to reduce the tax burden of massive corporations doing precisely what Apple did so as to attract them to incorporate their European headquarters in Ireland in the first place.

Ireland denies the accusations to this date. Apple, likewise, keeps insisting it paid every cent in taxes it oved over the disputed period. Vestager’s investigators repeatedly made it clear they believe the two colluded. In reality, all three are probably right, but it’s one thing to suggest Ireland may have dabbled into a rarely encountered level of corporate-friendly legislative activism with no regard for its allies, based on some bafflingly cynical views of the EU as a whole. It’s a whole other thing to prove any of that in the court of law beyond reasonable doubt.

In fact, this outcome is what many industry watchers have been warning about for years, repeatedly claiming that trying to essentially extort one of the world’s largest companies out of an eleven-digit figure in back taxes it supposedly owes across more than a decade’s worth of business activity could, perhaps, one day come back to bite the Competition Commissioner’s office. After all, there’s hardly much difference between tax avoidance and fulfilling one’s fiduciary duty: Apple played the cards it was given as well as it was legally allowed to and tax is one of those things where you just stick to the rulebook.

As Vestager can attest, retroactively changing the rulebook with the intent of taxing one’s goodwill or lack thereof isn’t really a feasible undertaking as it requires subjects willing to pay above and beyond what they owe; even entities advocating for higher taxes do so separately of their tax filings, i.e. only paying more after successfully lobbying for legislative changes dictating that to be the case.

A whole other issue is how Vestager might or should treat Ireland in the aftermath of this massive blow. Because the whole point of the EU has nothing to do about any given state member’s effective tax rate; the European Union is all about the friends we make along the legally gray way of avoiding that rate of taxation.